The electric drive of an elevator attends to the moving of an elevator car in an elevator hoistway between stopping floors. The control system of an elevator forms the target value for the speed of the elevator car, i.e. the speed reference, for the electric drive.
The electric drive comprises the hoisting machine of the elevator, which hoisting machine comprises an electric motor, which nowadays is usually an alternating-current motor. The electrical energy supplied to the stator in the electric motor is converted into rotational energy of the rotor, and conversely the rotational energy of the rotor is converted back into electrical energy during motor braking. The hoisting machine also comprises a traction sheave, which is mechanically attached to the rotor or to the shaft of the rotor. The elevator car is suspended in the elevator hoistway with ropes passing via the traction sheave, and moving force is transmitted from the traction sheave to the elevator car via the suspension ropes.
An electric drive often also comprises a separate power supply device, e.g. a frequency converter, with which the power supply between the electricity network and the hoisting machine of the elevator is adjusted. By adjusting the power supply between the hoisting machine and the electricity network, the speed of the elevator car can be changed steplessly.
An electric drive is generally taken into use already at an early stage during the construction or modernization of an elevator, because the elevator car to be moved with the electric drive can be used for the installation work to be performed in the elevator hoistway.
When installing an electric drive the hoisting machine of the elevator is fixed into the position reserved for it in the machine room or in the elevator hoistway. The frequency converter is connected to the supply cables of the hoisting machine and to the electricity supply of the building. The hoisting machine can be fixed to a special machine bedplate, or it can also be fixed e.g. to the guide rail of the elevator car or of the counterweight in the elevator hoistway.
When the electric drive has been installed into its position, a startup must still be performed for it by setting, among other things, the directions of movement of the elevator car and also the control parameters of the electric drive such that the elevator car can be driven in the desired directions in a controlled manner according to the speed reference. An elevator fitter sets the directions of movement of the elevator car generally visually by driving the hoisting machine with the frequency converter and by inspecting the direction of rotation of the traction sheave of the hoisting machine. The fitter can also directly inspect the direction of movement of the elevator car to be moved in the elevator hoistway, but this can be awkward, especially in the types of elevator systems in which the hoisting machine and the frequency converter are disposed in a machine room from where there is no direct line of sight into the elevator hoistway. Based on his/her observations, the fitter connects the drive direction of the frequency converter and the direction of movement of the elevator car to each other such that the elevator car can be driven in the detected drive directions with the frequency converter. This connecting can be done e.g. by manually entering data about the direction of movement of the elevator car from the user interface of the frequency converter.
This type of startup of an electric drive, to be performed visually and manually, complicates and slows down the installation work of an elevator. In addition, the risk of human error increases. Often an electric drive is also installed in its entirety in the elevator hoistway, in which case a fitter must perform the startup of the electric drive from the elevator hoistway, which increases the danger attached to the work.